1. Field of the Invention
The present invention relates to a liquid crystal display device and a projection type liquid crystal display apparatus using the liquid crystal display device.
2. Description of Related Art
The projection type display apparatuses, such as liquid crystal projectors, are roughly classified into a three-plate type and a single-plate type.
As disclosed in, for example, Japanese Unexamined Patent Application Publication No. S60-169827, the three-plate type projector divides light emitted from a light source into red (R), green (G), and blue (B), and modulates these color lights by using three light bulbs constructed from liquid crystal display device (hereinafter referred to as “LCD”), and then recombines the modulated color light beams and enlarge-projects the recombined color light beams onto a projection surface. This system requires a large number of components including these three LCDs, which results in a cost increase.
On the other hand, the single-plate type projectors require a single LCD, thereby achieving a reduction in cost.
General single-plate type projectors employ a method of enlarge projecting onto a screen by using the color filters as disclosed in, for example, Japanese Unexamined Patent Application Publication No. S59-230383. The advantages of this method are a simple optical system configuration, low cost, and a compact in design.
However, the technique reduces efficiency in light usage due to the optical absorption or reflection of the color filters, thereby making it difficult to achieve high luminance. The technique may degrade the image quality since the color filters composed of resin or the like have poor light resistance.
To solve the drawbacks, the single-plate type display as disclosed in Japanese Unexamined Patent Application Publication No. H4-316296 has been proposed. Specifically, a light source is divided into light beams of red, green, and blue by a dichroic mirror, and these light beams are then entered into a micro lens array at different angles so as to be distributed into their corresponding display pixels.
This display system enables a considerable improvement of light utilization efficiency, thereby providing a display apparatus having a high luminance.
In terms of light resistance, no color filter is used, and a polyimide film and an inorganic film each having high light resistance are used as alignment films, making it possible to obtain a display apparatus having a long life.
As the light bulbs mounted on the liquid crystal projector and the like, an active-matrix LCD driven by thin film transistors (hereinafter referred to as TFTs) is generally used.
Nematic liquid crystal is used in almost of the active-matrix LCD. The display system thereof is, for example, twisted nematic (TN type) liquid crystal having a 90-degree twisted molecular orientation.
Recently, vertical alignment (VA type) liquid crystal elements are considered in order to achieve high luminance, high contrast, high definition, and long lifetime of liquid crystal projector apparatuses. The vertical alignment type liquid crystal display devices are applicable to both transmission type and reflection type, and it seems to become a mainstream liquid projector, as well as inorganic alignment films for achieving a long lifetime.
In two substrates each having an alignment film formed thereon, these alignment films are arranged opposite each other and bonded together by applying sealing material onto the periphery of a display area for displaying image data. A liquid crystal cell is manufactured by forming a spacer to control the substrate spacing and sealing liquid crystal thereinto. The liquid crystal is composed of several types of monolithic liquid crystal materials, which is also called liquid crystal composition. A liquid crystal display device is manufactured by mounting a polarizer on the manufactured liquid crystal cell.